I doubt that most codes would address your situation and unless you install a separate vent there is nothing you can do about #2 either. he moisture is not as much of a problem as the reduced air flow when two units try to use a pipe designed for one.

: i am in an apartment complex, and i recently bought a washer and dryer. i've discovered that my upstairs neighbor's dryer vent is connected either directly or indirectly to mine. if i leave my dryer door open when she is drying clothes, my apartment fills with warm moist air and my dryer's filter accumulates lint on the "wrong" side. closing the dryer door keeps the air from her dryer out of my apartment, but i fear that even more condensate accumulates in my dryer.

: i have two questions:: 1. is this legal, and in accordance with most codes?: 2. how can i protect my dryer from the effects of this added moisture?